1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive film type device, and a piezoelectric/electrostrictive porcelain composition constituting the device, particularly to a small-sized piezoelectric/electrostrictive film type device which includes a dense piezoelectric/electrostrictive portion having remarkably high piezoelectric characteristics, which is superior in vibration transmission properties between a substrate and the piezoelectric/electrostrictive portion, which is suitable for an actuator, a sensor, and the like, and which has high characteristics, and a piezoelectric/electrostrictive porcelain composition constituting the device.
2. Description of Related Art
A piezoelectric/electrostrictive film type device has heretofore been known as a device which can control a micro displacement in the order of submicrons. Especially, a piezoelectric/electrostrictive film type device including a piezoelectric/electrostrictive portion constituted of a piezoelectric/electrostrictive porcelain composition and an electrode portion to which a voltage is applied stacked on a substrate formed of a ceramic is suitable for the control of the micro displacement. Additionally, the device has superior characteristics such as a high electric/mechanical conversion efficiency, high-speed response, high durability, and small power consumption. Therefore, the device has been used in various applications such as a piezoelectric pressure sensor, a probe moving mechanism of a scanning type tunnel microscope, a rectilinear guide mechanism in an ultra-precision processing apparatus, a servo valve for a hydraulic control, a head of a VTR apparatus, a pixel constituting a flat panel type image display apparatus, and a head of an ink jet printer.
Moreover, the piezoelectric/electrostrictive porcelain composition constituting the piezoelectric/electrostrictive portion has variously been studied. For example, a Pb(Mg1/3Nb2/3)O3—PbTiO3—PbZrO3 ternary solid solution system composition, or a piezoelectric/electrostrictive porcelain composition in which a part of Pb of the composition is replaced with Sr, La, or the like has been disclosed (e.g., see Japanese Patent Publication Nos. 44-17103 and 45-8145). It has been expected that a piezoelectric/electrostrictive device including a piezoelectric/electrostrictive portion which has superior piezoelectric characteristics (e.g., piezoelectric d constant) and which is a most important element for determining the piezoelectric characteristics of the piezoelectric/electrostrictive device.
However, in the conventional piezoelectric/electrostrictive device, a piezoelectric/electrostrictive material constituted of the piezoelectric/electrostrictive porcelain composition is formed on the substrate, and then, they are thermally treated to manufacture the piezoelectric/electrostrictive device. Therefore, even if it is tried to make the piezoelectric/electrostrictive porcelain composition contract to be densified by the thermal treatment, the substrate does not easily contract, and therefore density of the piezoelectric/electrostrictive portion lowers. This has caused a problem of low flexural displacement or dielectric breakdown in a portion having a low density at the time of application of the voltage. Especially, in a multilayered piezoelectric/electrostrictive device, the problem is remarkable, and there has been a strong demand for solving the problem.
Under this situation, as the conventional piezoelectric/electrostrictive device, a device has been disclosed in which the piezoelectric/electrostrictive portion obtained by thermally treating the piezoelectric/electrostrictive material formed of the piezoelectric/electrostrictive porcelain composition beforehand is attached to the substrate to densify the piezoelectric/electrostrictive portion (e.g., see Japanese Patent Application Laid-Open No. 11-29357).
However, in this piezoelectric/electrostrictive device, an inorganic/organic adhesive needs to be used in attaching the piezoelectric/electrostrictive portion to the substrate. Therefore, the adhesive hampers vibration transmission between the substrate and the piezoelectric/electrostrictive portion, or adhesive components deteriorate characteristics of the piezoelectric/electrostrictive portion or the substrate in some cases.
Further, it has not been considered at all that composition of the piezoelectric/electrostrictive porcelain composition is varied depending on each piezoelectric/electrostrictive portion in constituting the conventional piezoelectric/electrostrictive device when it is multilayered, and sufficient piezoelectric/electrostrictive characteristics are not necessarily obtained.
On the other hand, the piezoelectric/electrostrictive material of a bulk member has heretofore been manufactured by firing a predetermined piezoelectric/electrostrictive porcelain composition under predetermined temperature conditions. However, the piezoelectric/electrostrictive material needs to be sinterd at a sufficiently high temperature (e.g., 1200° C. or more) in order to manufacture the piezoelectric/electrostrictive material having desired superior piezoelectric characteristics. Therefore, there have been problems in equipment, cost, and the like.